US2598474A - Furnace with sectional radiant tube - Google Patents

Description

May 27, 1952 E. w. WEAVER 2,598,474

FURNACE WITH SECTIONAL RADIANT TUBE Filed June l1, 1949 IN VEN TOR.

Mh/ayer BY Ol @U5/wey Patented May 27, 1952 2,598,474 FURNAGE WITH sEcTloNAL RADIANT TUBEr` Ernest W, Weaver, Toledo, Ohio, assigner .to Sur,-

fade Combustin Corporation, Toledo, Ghipzwa ApplicationJunell, 1949, Serial No. 98,521 1 nains..` (o1. 15a-,1)v

AThis invention relates to a fuel red radiant tube for use in a furnace chamber and more Darvticularly to a radiant tube which is comprised.

of. refractory Itubular sections arranged in end toend relation between-.the side wallsof ka furnace chamber; tional refractory tube fromk collapsing .at the. joints is to provide a. supporting meansbeneath each joint. the supporting means usually v ta-Ising4 the/form ofl roof supported hangers or floorv supported piers depending Qn the, location oi the tube. Upon the heating and cooling of the iure nace, the relative expansion of such Joint; ,Suu-

portingL meansp-laces stress on. the tulle aieapd;

joints tending to. oueuthe tube at theioints and thereby.Y to shorten the. eiieotive life .of the tube. Moreover in addition toi bei. .grill adapted,to supporta, sectional. .tube at. the joints between. the Sec-tions, roofA .s.upiwrtedl hangers are relatively expensive to install audmaiutaiii- The present invention has for its object. toV provide for the supportof aseetioual radiant tube in a manner not requiring th e of any Isin@ of supporting `e the ends of. ille tube A of what I Consider to he novelarid my ,ation attention is .diie-,flied to the following specification and the claims ap.- needed,thereinE 'llie-areseatiuventioa is based on the `realizaieii that by the application of compressive Stress ii isv possible to maise'loiis spans of multiple seotionssafelv Supiieiitlieir ewan/aient- S-.eme .refaeiorv materialssueh aS bonded are available for use ai hielo temps which cannot eoonomieally be formed, sizes or shapes required for specialA aprile tions suchas radiant-tubes, and have great compressive-V .strength but little if any` 4dependable tensile strength. The present invention makes use of suon material to ferm a Seeiieaal radiant tube the.l

sections of which are held together by compressive force.

a lintel type of structure with vertical supports at the 'extreme' ends andfgravityf forces acting along the entire structure, therel is a couple formed by the force applied' at a vertical support and the equal force of gravity applied. at the location of the resultant of. those gravity forces, The magnitude, or moment, of the couple so formed is equal to the product ofthe Ysaldresultant force and the distance between it andY the supporting force. There will also be an equal and opposite couple formed at the other end of the lintel structure. If the lintel were cut at the center point, both sideswould move, both turn- 'lihe usual wayoi preventing a: see:y

n Carbide.

2;. ing,Y and; downward; It is` the application, ofv equal and opposite couplesthat maintains -astatic, or motionless, structure.

At the center of the uncut lintelstructure, there must be internal forces to opposel'fhe.ex#` ternally applied couples, and these internal. forces are suppliedlby the strengthof thematerials, with part of the forces in tension and; part ofv thev forces in compression. If an overall axial, comeA pressive force is applied to the lintel structure' in addition to the couples. already plieserft,A the' compressive forces may be increased andthe tem sile forces reduced to zero, or even changed: to small compressive forces. Without destroying the intern-al1 couple already presen-ff,-v

The present invention is based .on applying' sufiicientcornpressive forcesk to such a structure. to eliminate all tensile stress ill the structure. It is then possible to use an unbonded: joint allow the couple formed .by they eompressiv .prees to support the joint.

rhere is required, of. course, a certain: sheel'- strength in the materialv and V4at the j oints,but this streng-th is present; in materials of -thez class; described, and the forces; of friction will. supplythe required shear strength fatl the joints; isr a. precaution, how-ever, it i-s preferred to provide .a shear surface at the jointslsuoh asan.olfsefaconeh or spherical ball joint, the-offset joint being illusotrated in Fig. 2.

When utilizing compressive stresses and ,the couplev of forces at' the joints for-support there isf no longerne-ed for individual support of the joints of thetubes, and in fact such supports constitute. a hazard by their te-ndency'to expand and more: the joints out o-f alignment, with the.l result of leakage at Athe joints and danger of collapse of the tubes. by the present invention has speciall .utility in furnaces. such asthe catenary strip heatingffur` nace vwhich requires no conveyor? Within `the furnace, and furnaces with internally cooledl metal conveyors which are operated at very high temperatures', or in processes such as the gas pickling process, where the furnace atmosphere. or temperature is such thatmaterials. usedizlor` radiant tube hanger or pier supports cannot withstand furnace conditions and' non metallicsectional `radiant tubes are especially .wellsnited -to such conditions,

The principle of preventing propagation ofv hair line cracks and maintaining gas tight. retortsein' non-,metallic materials is disclosedthe patent: toV C. E; Hawke, 2,06-7085', but thesupport; ofaa structure by the use of compressive stressoren' The improved radiant tube providedv predetermined and arranged .parting lines, eliminating the necessity of external supports `at such parting lines or joints, is not disclosed therein. The use of springs or hydraulic means to apply the stress allows room for expansion to take care of thermal expansion and permanent growth, and maintains the required dynamic balance. This makes possible longer spans without individual joint supports.

In the drawing- Fig. l is vertical cross sectional View of a disc type sheet annealing furnace embodying the invention.

Fig. 2 is a fragmentary sectional view of a portion of the radiant tube at one of its joints.

Fig. 3 is a somewhat enlarged View of the burner head shown in Fig. 1.

The furnace with which the improved radiant tube has special utility comprises a horizontally elongated furnace chamber defined by side walls l, a floor l and a roof l2, all within a metal frame work I3 comprising upright side beams I4, top cross beams I5 and bottom cross beams I6. 'Ihe work to be heated, namely, sheet metal plates I1, is advanced through the furnace on a disk type roller hearth, the disks being indicated at I3 and being mounted on power driven shafts 2B whose ends extend through the side walls I0 of the furnace chamber. The disks or adjacent shafts are in staggered relation as indicated by reference numeral 2|.

A bottom row of radiant tubes is indicated at 22 and an upper row of the same at 23. The tubes of the bottom row have a somewhat smaller cross sectional area than the upper tubes but other- Wise the tubes are the same and therefore a detailed description of one will suflice for all.

Each radiant tube is comprised of tubular sections, arranged end to end with offset joints 24 (see Fig. 2) to assist in assembly and alinement of the sections. In Fig. l the tube is shown as comprised of five tubular sections with the middle section substantially longer than the end sections. The tube extends across the furnace chamber and is maintained in compression between its ends by means comprising a spring pressed member 25, the spring being indicated at 26. The member 25 presses against an annular burner head 21 which in turn presses against an annular metal spacer 28 which in turn abuts the adjacent end of the radiant tube. At its opposite end the tube abuts an annular fixture 39 which is backed by the adjacent parts of the metal frame work I3. Products of combustion are exhausted from the radiant tube by an eductor 3| which connects with the discharge end of the tube by a tubular extension 32 whose inner end projects into the annular fixture 36.

The burner head 2l has an annular gas supply chamber 33 to which fuel gas is delivered by a supply pipe Sil, the gas issuing from said chamber 33 through a ring of gas discharge ports 35 which are inclined to discharge towards a point near the front end of the radiant tube. The central aperture 36 in the burner head constitutes an inlet for the admission of atmospheric air for supporting combustion of the fuel issuing from the burner head ports 35. The eductor 3l produces enough partial vacuum in the radiant tube to induce air at atmospheric pressure to flow through the said central aperture 36. The fuel thus issuing from the ports 35 may be ignited by flame from a premix pilot burner 3l which projects into said aperture 36 from a support not shown.

The springs 26 are held in adjusted compression by means of adjusting nuts 38 on the outer ends of rods 40 whose inner ends are anchored to the metal frame work I3. The springs 25 are maintained under such degree of compression that the radiant tube will not collapse at the joints of its tubular sections.

From the foregoing description it will now be seen that the present invention provides a radiant tube assembly that is well adapted for its intended purpose.

What I claim as new is:

1. A furnace comprising structure defining a furnace chamber, a horizontally extending tubular heating element disposed in said chamber, support means attached to said structure for vertically supporting said element at the ends thereof, said element comprising tubular sections in abutting end to end relation, and means for maintaining said sections in axial alignment consisting of means supported on said structure for maintaining said element under compressive stress sufficient to produce compressive forces across the adjoining faces of the abutting ends of the tubular sections, thereby vertically supporting the entire element in the furnace chamber between support means.

2. In a furnace having a chamber to be heated, in combination, a radiant tube in said chamber defined by an assembly of tubular sections in end to end relation, means carried by said furnace for maintaining said tube under suicient longitudinal compression to maintain axial alignment of said sections, and structure defining two vertical supports for supporting said tube.

3. In a furnace according to claim 2, the combination which comprises wall means defining a furnace chamber between said supports through which said tube is adapted to extend whereby to supply heat to said furnace chamber.

4. In a furnace according to claim 2, the combination which comprises a gas supply head at one end of said tube for feeding fuel thereinto for combustion therein and exhaust means at the other end of said tube for producing a draft through said tube, said head and draft means being supported on said supports.

5. In a furnace according to claim 2, the combination which comprises an annular head at one end of said tube for feeding fuel thereinto for combustion therein, and means carried by one of said supports for applying longitudinal compression to said assembly through said head.

6. In a furnace according to claim 2, the combination which comprises means carried by one 0f said supports for applying longitudinal compression to said assembly, an annular fixture carried by the other of said supports for receiving thrust from said assembly, and means carried by said other support for producing draft through said tube 7. In a furnace, in combination, structure dening two laterally spaced supports, a radiant tube adapted to extend between said supports, the said tube being defined by an assembly of tubular sections in end to end relation and being supported only at its ends, and means carried by said structure for maintaining said assembly under longitudinal compression sufficient to maintain said sections in axial alignment.

ERNEST W. WEAVER.

(References on following page) REFERENCES C'I'ED The following references are 0I" record in the file of this patent:

Number Hamlnk Sept. 7, 1937 Number Number Name Date Munford Sept. 14, 1937 Hess Jan. 18, 1938 Vaughan Feb. 7, 1938 Ruckstahl Nov. 5, 1940 Hamlnk Nov. 11, 1941 Stookey June 7, 1949 FOREIGN PATENTS Country Date Great Britain Oct. 2, 1944

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